add dummy hello world

codex-rs/README.md

@@ -103,3 +103,7 @@ This folder is the root of a Cargo workspace. It contains quite a bit of experim
 - [`cli/`](./cli) CLI multitool that provides the aforementioned CLIs via subcommands.
 
 If you want to contribute or inspect behavior in detail, start by reading the module-level `README.md` files under each crate and run the project workspace from the top-level `codex-rs` directory so shared config, features, and build scripts stay aligned.
+
+## Dummy Hello World
+
+Hello world.